A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of preparing for a marathon. It sets up the overall theme of training. It does not refer to any previous information. Why other lines are not chosen? Paragraph 2 starts with "To avoid injuries..." which is not a general statement. Paragraph 3 starts with "On the day before the race..." which assumes prior context. Paragraph 4 starts with "After months of training..." which also assumes prior context. Paragraph 5 starts with "Monitoring your progress..." which is not a general statement.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it gives final advice for the day before the race. It wraps up the training process and focuses on what to do right before the marathon.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because the second paragraph gives advice on how to improve performance, which follows the idea of setting a training schedule.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because monitoring progress is important after incorporating strength training. It shows a logical flow of ideas.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because after monitoring progress, it is time to taper off runs. This shows a logical order in the training process.
• Pair 4 (Paragraph 4 → Paragraph 5): This pair connects because tapering off leads to the final preparations before the race, which includes hydration and nutrition.